IMAGING APPARATUS AND IMAGING METHOD

• US 20090015690A1
• Filed: 07/07/2008
• Published: 01/15/2009
• Est. Priority Date: 07/09/2007
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Yamashita, Yuichiro
• Granted Patent: US 7,990,433 B2
• Time in Patent Office: Days
• US Class Current: 348/229.100
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene
• CPC Class Codes: H04N 23/71 Circuitry for evaluating the brightness variation
• CPC Class Codes: H04N 23/73 by influencing the exposure time
• CPC Class Codes: H04N 23/741 by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors

Abstract

The object is to determine an appropriate light exposure condition thereby to generate an appropriate synthesized image signal for an imaging scene for which an appropriate light exposure condition cannot be obtained by conventional techniques. There is provided an imaging apparatus including: a light exposure condition determining unit for determining a plurality of light exposure conditions based on a histogram of the luminance distribution of an imaging scene; an imaging unit for imaging, at plural times, the imaging scene under the plurality of light exposure conditions determined, and generating a first raw image signal and a second raw image signal; and an image synthesizing unit for synthesizing the first raw image signal and the second raw image signal using, as a boundary, a reference value in the first raw image signal to generate a synthesized image signal, wherein the light exposure condition determining unit determines at least one light exposure condition of the plurality of light exposure conditions so that the reference value in the first raw image signal corresponds to the luminance value at the bottom of a ravine of the histogram of the luminance distribution of the imaging scene.

Claims

1. An imaging apparatus comprising:

a light exposure condition determining unit for determining a plurality of exposure conditions based on histogram of a luminance distribution of an imaging scene;

an imaging unit for imaging, at plural times, an imaging scenes under the plurality of exposure conditions determined by the light exposure condition determining unit, and generating first and second raw image signals before synthesizing; and

an image synthesizing unit for synthesizing first and second raw image signals using, as a boundary, a reference value contained in the first raw image signal to generate a synthesized image signal, wherein

the light exposure condition determining unit determines at least one of the plurality of exposure conditions so that the reference value contained in the first raw image signal corresponds to a luminance value at a bottom of a ravine of the histogram of the luminance distribution of the imaging scene.

2. The imaging apparatus according to claim 1, wherein

the histogram of the luminance distribution of the imaging scene is formed by an imaging parameter weighting at a time of counting a frequency.

3. The imaging apparatus according to claim 2, wherein

the imaging parameter is a position in the imaging scene.

4. The imaging apparatus according to claim 2, wherein

the imaging parameter is a shape of an object in the imaging scene.

5. The imaging apparatus according to claim 2, wherein

the imaging parameter is a color of an object in the imaging scene.

6. The imaging apparatus according to claim 2, wherein

the imaging parameter is a movement of an object in the imaging scene.

7. The imaging apparatus according to claim 1, wherein

the light exposure condition determining unit determines a plurality of exposure condition candidates so that the reference values thereof correspond respectively to plural luminance values at bottoms of ravines of the histogram, and elect one as the light exposure condition from the plurality of candidates based on an evaluation function.

8. The imaging apparatus according to claim 7, wherein

the evaluation function is derived by calculating, in estimation, from the histogram, a number of pixels of a black fall or a white raise in the synthesized image signal generated using the plurality of light exposure condition candidates respectively.

9. The imaging apparatus according to claim 1, wherein

the light exposure condition determining unit changes, based on a number of pixels of a black fall or a white raise in the synthesized image signal estimated based on the histogram, a number of the light exposure conditions to be determined, and the imaging time by the imaging unit.

10. An imaging method comprising:

a light exposure condition determining step for determining a plurality of exposure conditions based on histogram of a luminance distribution of an imaging scene;

an imaging step for imaging, at plural times, an imaging scenes under the plurality of exposure conditions determined by the light exposure condition determining unit, and generating first and second raw image signals before synthesizing; and

an image synthesizing step for synthesizing first and second raw image signals using, as a boundary, a reference value contained in the first raw image signal to generate a synthesized image signal, wherein

the light exposure condition determining step determines at least one of the plurality of exposure conditions so that the reference value contained in the first raw image signal corresponds to a luminance value at a bottom of a ravine of the histogram of the luminance distribution of the imaging scene.